Controlling capillary fingering morphology in patterned porous media

We present a methodology to modulate immiscible fluid-fluid invasion patterns in patterned porous media during drainage in the capillary fingering flow regime. A 2D patternedporous medium is generated by a sequential deposition algorithm of disks/grains of twodistinct size ranges (dual-porosity media). To attain patterned porous media, selectedregions are packed with small grains, elsewhere packed with larger grains. By tuning theratio of viscous to capillary forces, as defined by the capillary number (Ca), we controlthe degree to which the underlying microstructure affects the invasion morphology in thepatterned porous medium. A decrease in Caamplifies the influence of the underlying porestructure, resulting in a more pronounced alignment of the flow pattern with the porousmedium’s geometry. For these “structured” flows, the drainage within zones packed withsmaller grains (having relatively smaller pores) is less than 10%. In contrast, an increase inCapromotes more “random” displacement patterns with significant invasion in fine (morethan 10%) and coarse pores. The possibility to modulate multiphase flows using patternedporous media can have practical implications in engineered membrane designs for fuelcells, selective transport, and filtering applications.